PART I CHAZYAN AND RELATED BRACHIOPODS—-COOPER 573 
and with the greatest convexity at about the middle. Anterior profile strongly 
arched. Fold originating about one-third the length from the beak, low and 
gradually widening anteriorly. Umbo slightly swollen with incurved beak. Flanks 
narrowly convex and with steep lateral slopes. 
Measurements in mm.—Holotype, length 11.6, brachial length 10.9, width 11.1, 
thickness 8.0. 
Type.—Holotype: 111153. 
Horizon and locality—Elway formation in Tennessee: 4 mile northeast of 
Eidson, Kyles Ford (T.V.A. 170-SE) Quadrangle. 
Elway formation in Virginia: On Virginia Highway 71, 1 mile northeast of 
Dickensonville, Hansonville (T.V.A. 205-SW) Quadrangle. 
Whistle Creek formation in Virginia: On Virginia Highway 602, 54 miles 
S. 82° W. of Middlebrook, Augusta County. 
Discussion.—This species is characterized by the numerous direct costae mark- 
ing the surface of the valves. It differs from C. indefinita in having its shell more 
evenly and regularly costate and in possessing 5 costae in the sulcus instead of 6 
as in C. indefinita. It differs from C. elliptica in the form of the valves, the latter 
being a much wider shell. 
CAMERELLA NUDA Cooper, new species 
Plate 115, C, figures 12-21 
Shell small for the genus, slightly longer than wide; oval in outline; apical 
angle slightly greater than a right angle; greatest width at about the middle and 
with narrowly rounded sides ; posterolateral margins sloping toward the middle; 
anterior margin truncated. Posterior two-thirds smooth; anterior third marked 
by distant and indistinct costae, 2 or 3 on the flanks and 3 in the sulcus. 
Pedicle valve moderately convex in lateral profile; broadly and gently convex 
in anterior profile; umbonal and median regions inflated; sulcus originating at 
the middle; sulcus moderately wide and with its floor gently convex; sulcus 
bounded by the two strongest costae on the valve; flanks swollen. Tongue mod- 
erately long and rounded. Beak low. 
Brachial valve with moderately convex lateral profile and strongly arched an- 
terior profile with steep lateral slopes. Umbonal and median regions swollen. 
Fold low and inconspicuous. Flanks swollen. 
Measurements in mm.—Holotype, length 6.2, brachial length 5.6, width 6.0, 
hinge width 1.0, thickness 4.4. 
Types.—Holotype : 117139a; figured paratype: 117139b. 
Horizon and locality—Murfreesboro formation in Tennessee: On Stone River 
just west of U. S. Highway 70S, 14 miles northwest of Murfreesboro, Murfrees- 
boro (15’) Quadrangle. 
Discussion.—This species is characterized by its smooth posterior half or three- 
quarters and the indistinct nature of the costae on its flanks and in the sulcus. 
The species is unlike C. immatura in having more costae and in having some of 
